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June 26, 1962
J. w. l. HEIJNIS
3,041,048
MELTING GRID
Filed March 7, 1960
INVENTOR.
J.W. l.
HEIJN IS
:4 w
ATTORNEY
f
United States Patent 0 ice
3,041,048
Patented June 26, 1962
2
1
paratus for melt spinning which obviates formation of
deposits within the spinning system.
3,041,048
MELTING GRID
Still another object of the present invention is to provide
a melt spinning system which may be operated for pro
longed periods of time without maintenance due to for
corporation of North Carolina
mation of deposits therein.
Filed Mar. 7, 1960, Ser. No. 13,340
A further object of this invention is to provide an ap
Claims priority, application Netherlands Apr. 6, 1959
paratus for controlling the temperature of a melt spinning
1 Claim. (Cl. 257—304)
system throughout various stages of the operation in order
This invention relates generally to an apparatus for the 10 to prevent buildup of deposits from degraded polymer or
other impurities.
manufacture of thread-like or ribbon-like products from
Gther objects and advantages of this system will become
thermoplastic linear polymers such as polyamides, poly
apparent upon study of the following detailed disclosure.
esters, or polyurethanes, and more particularly to an im
The foregoing objects may be accomplished, in accord
proved system for the grid spinning of such polymers
15 ance with this invention it the known systems are modi
under precise temperature controlled conditions.
?ed so that the grid inner wall, up to less than 3 cm. above
In this system, polymer in the form of granules, chips
James Watt Ijsbrand Heijnis, Arnhem, Netherlands, as
signor to American Enka Corporation, Enka, N.C., a
or shavings, is conveyed from a container through a
down pipe onto a melting grid comprising one or more
the upper side of the grid bars, is maintained at the same
temperature as these grid bars, if thereafter the tempera
heated grid bars and a heated grid wall, and subsequently
ture is permitted to recede over a height of less than 1
mm., and if the temperature thereabove is maintained be
is pressed in molten condition from a storage chamber
adjoining the grid bars through one or more spinning or
molding ori?ces by means of pumps, after which the
formed products are cooled and collected. The grid
inner wall adjoins the inner wall of the down pipe and
low the softening point of the polymer.
Surprisingly enough, it has been found that as a result of
these measures no
will form on the grid wall. Con
sequently, polymer granules can be melted and satisfac
25 torily spun according to this system for very much longer
forms a continuous surface.
periods of time than heretofore possible before the spin
In carrying out a known method similar to the type to
be described more fully hereinbelow, the melting grid is
heated to above the melting point of the polymer. This
may be accomplished electrically, although preference is
generallygiven to heating of the grid by means of gases
or vapours having a boiling point which coincides with
ning process must be interrupted due to declining yarn
quality.
The manner in which the upper portion of the grid wall
is kept below the softening temperature of the polymer
may be varied and accomplished in many different ways.
A most favorable condition is obtained, however, if the
grid inner wall, above the said receding or recessed portion,
which term will here be used to include chips, shavings,
is kept at a temperature below 150° C., and preferably
etc., initially fuses at the upper side of the grid bars and
flows as a mixture of highly viscous liquid and semi-fused 35 below 100° C., either ‘by gas or a liquid cooling medium.
If the grid wall at the point of the receding temperature
granules between the bars where 1a further heating and
portion is kept very thin, it is possible to realize a consid
fusing of the mass occurs. The melt is further homoge
erable drop in temperature over a height of less than 1
nized, in the storage chamber below the grid bars, prior
mm. It is necessary, however, to provide extremely effi
to being discharged by the spinning pumps.
A condition of equilibrium, dependent on temperature 40 cient cooling so that the heat consumption will not become
high. It is also possible to construct the grid wall, at the
of the grid bars and on the take-off rate of the spinning
point of the recess, as a membrane of great length and
pumps, sets in for the transition point or the region where
therefore of high heat resistance. However, this results in
the granules become melt. Small variations in the grid
the desired grid temperature.
The granular material,
a ?exible structure creating dif?culties in practical use.
If a multiple grid having an inner wall consisting of
tions in the pressure distribution in the granular mass 45
two sections is used, these dif?culties do not occur. The
above the grid, may give rise to ?uctuations of the transi
two sections should be ‘aligned and separated by an annu
tion point for this region. In the case of the heretofore
lar gap having a width of less than 0.5 mm., with the gap
known methods, these ?uctuations result in difficulties
being located at a height of 5 to 10 mm., preferably 8
since the melt may then creep up against the grid wall at
50 mm., above the upper side of the grid bars.
‘
diiferent and varying levels.
U.S. Patent No. 2,300,083, dated October 27, 1942,
On the other hand, a falling melt level may result. In
suggests supplying granular material along a non-heated
other words, fused polymer lags or stays behind on the
wall to a melting grid. The efforts discussed therein,
grid wall and is not removed therefrom before the melt
however, did not lead to the desired result either because
again reaches the same temperature level. This polymer
retains granules which in this manner are kept at a high 65 the measures described above were not applied, or only
temperature or in the take-off of the pumps, or modi?ca
temperature for a long period. All of the foregoing may
give rise to formation of a rim consisting of degraded
partially applied.
weak spot in the spun product.
The formation of the aforesaid rim from degraded
polymer or other impurities is also promoted if the tem
although the risk that a particle of dirt from the rim of
the melt will clog the spinning ori?ce is thereby increased.
The methods proposed herein lead to particularly bet
ter results if the polymer is supplied to the melting grid
or even carbonized polymer on the inner wall of the grid.
Moreover, when some of this polymer is released from the 60 under increased mechanical pressure. Increased pres
sure brings about a higher melt production per melt unit,
rim, this may cause a clogging in the spinning plate, or a
Moreover, an incrustation of dirt at the rim may become
detached more quickly clue to increased mechanical pres
’ perature of the grid wall is permitted to decrease in an 65 sure. Prevention of a dirt rim formation on the inner
upward direction. As a result, the granules descending
grid wall, in accordance with the present invention, em
along this wall gradually soften and ?nally remain stuck
phasizes the advantages of and permits use of this in
in a rim already or previously formed.
creased pressure without the accompanying disadvan
An object of the present invention is to provide a melt
tages.
spinning system not having the disadvantages of those 70 In addition to the method described, this invention
also relates to an apparatus comprising a container for
known systems enumerated above.
granules, a down pipe connected to the container, a melt
Another object of this invention is to provide an ap
3,041,048
ing grid consisting of one or more heatable grid bars and
a heatable grid wall, a storage chamber, one or more
spinning pumps, molding or spinning ori?ces, and a spin
ning cell, as well as a collecting device. These elements
should be functionally arranged one after the other in
the sequence stated, with the grid inner wall adjoining
the inner wall of the down pipe and forming a continu
ous surface.
A much preferred embodiment of this invention is ob
4
According to this invention, it has now been found that
the foregoing will not occur if the annular chamber is
?lled for the greater part by an annular element consist
ing of heat-insulating and heat-resistant material. As
bestos cement has been found to be very suitable for this
purpose.
Finally, the invention herein relates to one of the ap
paratus described hereinabove in which, however, a mem
ber is provided in the down pipe thereof for exerting a
tained if the grid inner wall, at a height of less than 3 10 pressure, in a manner known to this art, on the polymer
cm. above the upper side of the grid bars, recedes or is
mass in the direction of the melting grid. Such members
recessed for a distance of less than 1 mm. and if the wall
are known per se and usually are applied in the form of
portion below said receding portion adjoins a heating
system provided for the grid bars and the remaining wall
endless screws, propeller blades, rams, and the like. As
previously explained, dii?culties with regard to the use
portion is connected to a cooling system. The cooling 15 of pressure-exerting members are removed by the com
system of this preferred apparatus comprises an annular
bination of said members with the system described
conduit extending around the grid wall and having con
herein. In this way, the advantages obtained with the
nections ‘for the supply and discharge of a cooling me
dium. The medium may be any liquid, although it is
preferred to use water or gases. According to another
embodiment, which in a structural sense is somewhat
more di?icult to construct, but on the other hand pre
sents an additional advantage in that no connections to
a cooling medium circuit are required, consists in a cool
pressure elements are fully utilized without the disadvan
tages thereof.
The invention will be further explained and illustrated
below with reference to the accompanying drawings,
wherein
FIGURE 1 is directed to a cross-sectional view, in
elevation, of a preferred embodiment of this invention;
ing system having a series of axially directed cooling ribs
FIGURE 2 shows a vertical section on an enlarged
arranged around the melting grid. This embodiment is
scale of a portion of the apparatus appearing in FIG
illustrated and will be described fully hereinbelow.
URE 1; and
The shape of the portion of the grid inner wall where
FIGURE 3 is drawn to a detail of FIGURE 2 on a
the temperature recedes (the receding or recessed por
still more enlarged scale.
tion) is important for satisfactory functioning of the ap 30 In FIGURE 1, reference numeral 1 denotes a melting
paratus. At that point the wall should be so constructed
grid having an annular mantle 2 which is provided at two
that with the simplest possible auxiliary means, and with
opposite sides with ?uid conduits 3 and 4. By means of
the least possible loss of energy, the large temperature
these conduits, the melting grid is connected to a device
drop over the height of the recess may be realized. It
(not shown) for the supply of a heating medium. Within
has already been stated that a very ‘thin construction of 35 the annular mantle 2 and connected thereto on both sides,
the wall, or construction as an elongated membrane pre
there is provided a system of tubes 5 which constitute
sents di?iculties. These difficulties are obviated herein
grid bars through which the heating medium ?ows. At
by forming the grid of multiple construction, or with the
the upper side thereof, annular mantle 2 borders on a
inner wall thereof consisting of two portions in registry
cooling ring 6 and is sealed thereto through a silver ring
one with another and separated by an annular gap hav 40 7. The cooling ring 6 and the mantle 2 are secured in
ing a width of less than 0.5 mm., said gap being located
sealed relationship by means of elongated bolts 8.
from 5 to 10 mm. (preferably ‘8 mm.) above the upper
A down pipe 9 is secured on the melting grid 1 by
side of the grid bars. In this way the gas present in the
means of bolts 19. Nipple 11 is ?xed in the side wall
gap forms an insulation between the cold and hot por
of this down pipe and may be connected through a suit
tions. of the grid inner wall.
able conduit (not shown) to a source of nitrogen by
It is true that a transport of heat may still occur be 45 means of which the oxygen is forced out of the down
tween the cold and hot portions as a result of radiation
pipe and therefore out of the polymer present therein,
and/ or heat conduction by the gas medium. This heat
all as is known in this art. Below the tubes or grid bars
transport, however, is very small relative to the metallic
5 and in the mantle 2 there is provided a collecting hopper
heat transmission of the grid inner wall per se. Further,
12. FIGURE 2 shows the manner in which this collect
it has been found that a particularly effective heat in~
ing hopper is ?xed by means of bolts 13 against a seat 14
sulation is obtained if the annular gap connects at the
of the annular mantle 2. The hopper 12,, which is con
outside to an annular chamber one of the walls of which
structed as a solid block, is provided with a discharge
is so constructed that the, cooled portion of the grid
opening 15 so dimensioned that the melt of the polymer
inner Wall extends as a tapering lip towards the gap. The
to be spun by this apparatus barely ?ows under the in
annular chamber appears to check considerably the heat 55 ?uence of its own weight, or by hydrostatic pressure. The
conduction by the gaseous medium, but as a consequence
collecting hopper has a ?at bottom surface 16 with which
thereof the length of the metallic connection between the
it ?ts ?ush against the flat upper surface 17 of a pump
cold and hot portion of the grid inner wall is extended.
block 18. In this way an excellent heat transfer between
This causes a higher thermal resistance between these
the hopper and the pump block is obtained.
two portions.
60
The melting grid 1 and the pump block 18 are inter
It has now been found that in the case of large ?uc
connected by means of bolts 19. These bolts also main
tuations in grid temperature, which may occur for exam
tain the discharge opening 15 of collecting hopper 12 in
ple, during heating or cooling of the grid, the annular
registry with the entrance 20 of a suction line 21 through
chamber may, as it were, breathe. Breathing, as used
which molten polymer is supplied to spinning pump 22.
herein, is intended to mean production of a stream of 65 Pressure line 23 leads from the pump to a sand ?lter 24
gas through the gap from or towards the chamber due
provided above a spinning plate 25. The pump block is
to an expansion or contraction of the generally inert gas
surrounded by a heating jacket 26 through which shaft 27
>
of the spinning pump is passed.
If breathing is not prevented, polymer melt may be
To the upper edge 28 of the down pipe 9 there is
drawn into the annular chamber, along with the incom 70 secured a radially projecting ?ange 29. . Between the
ing gas, where. it eventually will become degraded or
flange 29 and a counter ?ange 30' the lower end of a
carbonized. In the case of a gas stream moving toward
rubber sleeve 31 is clamped. The upper edge of sleeve
the outside of the chamber, the impurities thus formed
31 is clamped between ?anges $2 and 33, the latter of
may then be forced into the melt where they will disturb
which is connected by means of bolts 34 to a ?ange 35
the. spinning process.
75 of a granule cock 36. This cock is adapted to close the
therein.
3,041,048
discharge opening of a ?xed granule bunker 37. In the
closed position of cock 36 nitrogen gas may escape from
the down pipe through a bypass 38 to the granule bunker.
In order to guide divided polymer from the granule bunker
37 through the cock 3'6 to the down pipe 9 there is con
nected to the ?ange 33 a coaxial length of tube 3&3 which
extends into the down pipe 9. To facilitate replacement
of the melting grid 1, the down pipe 9‘ connected there
with is provided with an annular handle 40. During the
spinning process, which can be more clearly understood 10
with reference to FIGURE 1, the spinning apparatus is
mounted on top of a spinning box 50 of the usual type.
Only the top of this box has been shown.
FIGURE 3 illustrates in particular the connection of
annular mantle 2 to the cooling ring 6. Reference nu 15
meral 41 denotes the lower rim of the cooling ring which
extends downwardly ‘as a tapering lip. Between this lip
41 and the mantle 2 there remains a gap ‘42 located at a
height of 8 mm. above the tubes 5 and having a gap
width of 0.4 mm.
An annular ?lling element 43, made of pressed asbestos
cement, ?ts into an annular chamber between the lip 41
and the mantle 2, behind the gap 42 as shown. The ?ll
ing element borders at the outer side on the extended
outer wall 44 of the mantle 2, which through silver ring 25
7 is connected in sealed relationship to the cooling ring 6.
The cooling ring and mantle are drawn tightly together
by bolts 8 so that the silver ring flows and the ?anges
47, ‘48 contact each other.
The outer wall 44 is illustrated as ‘being thin at the point 30
of the ?lling element 43 in order to form a high thermal
resistance. Rim ‘49 raises ?lling cement 43 and provides
a small open space '45 at the level of gap 42. This space
45 serves as a collector for impurities which might pos
sibly pass through the gap 42. The ring 6 is cooled by
thirty-two cooling ribs‘ ‘46, shown more clearly in FIG
URE 2, which ribs are equally spaced circumferentially
therearound.
According to another possible embodiment, the cooling
ring may be formed hollow with supply and discharge 40
conduits through which coolants may be circulated.
Water, for example, may be passed through the hollow
ring. Both the air-cooled and the water-cooled embodi
ments of the cooling ring, however, provide means for
45
cooling the lip 41 down to less than 100° C.
When using the apparatus for the melting and spinning
of polyamide granules having dimensions of about 3
mm., it has been found possible to operate for approxi
mately three months without interruption. After disman
tling the apparatus and opening the grid it was found that 50
dirt had not accumulated anywhere and that a rim of
impurities had not been formed. In this connection, it is
to be noted that the average operating time of the melting
grids in he known embodiments amounts to two to three
weeks, after which further spinning usually is impossible 55
due to the formation of a rim of dirt or other material.
6
Inasmuch as other embodiments and alternatives will
become apparent to those skilled in this art, it is intended
that the scope of this invention be limited only to the
extent set forth in he following claim.
What is claimed is:
A melting grid comprising:
(a) an annular mantle, said annular mantle having a
vertical outer wall with a main body portion of one
thickness and an upper portion of reduced thickness,
21 vertical inner wall extending coaxially with but
terminating below the upper portion of said outer
wall, upper and lower closure means extending
radially outwardly from the terminal ends of said
inner wall to connect the same with said outer wall
and thereby form an annular heating zone without
enclosing said upper portion of the outer wall, and
tubular grid bars secured to the mid-portion of said
inner wall and communicating with said annular heat
ing zone;
(b) An annular cooling ring resting in coaxial relation
ship on the upper portion of said outer wall, said
annular cooling ring having a lower lip projecting
downwardly in overlapped relationship with the up
per portion of said outer wall to de?ne ‘an annular
chamber for separating the outer wall of said annular
mantle from the annular cooling ring and terminating
above the inner wall of said annular mantle to de
?ne an annular air gap for separating the cooling
ring from the inner wall of said annular mantle, said
cooling ring having an inner surface coextending with
that of said inner wall, the inner wall of said an
nular mantle extending above the upper surface of
said grid bars by less than 3 centimeters, and the an
nular gap de?ned by the lower lip of said annular
cooling ring and the said inner wall being less than
one millimeter in vertical height;
(0) a plurality of cooling ribs secured to and extending
radially outwardly from the periphery of said annular
cooling ring to lower the temperature of said lower
lip;
(d) an annular rim projecting upwardly from the
outer edge of said upper closure means to de?ne an
annular air space interconnecting said annular cham
ber with said annular air gap;
(e) insulating means supported by said annular rim
and substantially ?lling said annular chamber; and
(f) means for raising the temperature in said annular
heating zone and the grid bars communicating there
With.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,253,089
2,300,083
2,773,923
Nydegger ____________ __ Aug. 19, 1941
Worthington __________ __ Oct. 27, 1942
Smith _______________ _- Dec. 11, 1956
:UNITED STATES PATENT OFFICE
CERTIFICATE OF CORRECTION
Patent No. 3,041 ,048
June 26, 1962
James Watt Ijsbrand Heijnis
It is hereby certified that error 8.
ant requiring correction and that the sa ppears in the above numbered pat
id Letters Patent should read as
correoted below.
In‘the grant, line 3, and in the heading to the printed
specification, lines 4 ‘and 5, for "a corporation of North
Carolina‘i", each occurrence, read -- a corporation of Delaware
Signed and sealed this 19th day of February 1963.
(SEAL)
Attest:
ESTON G. JOHNSON
Attesting Officer
DAVID L. LADD
Commissioner of Patents